GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon - 2WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P1431 Fuel Level Sensor 2 Performance

Object Number: 664670 Size: MF
Engine Controls Component Views
FPR, Fuel Pump/Sender, Fuel Tank Pressure Sensor, G403,G102
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The rear fuel level sensor 2, mounted in the rear fuel tank, measures fuel level changes within the rear fuel tank. The Fuel Level sensor 2 has a signal and a ground circuit.

When the fuel level is high the sensor signal voltage is high. When the fuel level is low the sensor signal voltage is low.

The PCM uses inputs from the fuel level sensor 1 and the fuel level sensor 2 in order to calculate the total fuel remaining in both fuel tanks. The system sends this information via the serial data to the IPC. This information displays on the fuel gauge.

This diagnostic tests for a stuck fuel level sensor 2 signal. If the PCM determines that the fuel level (rear tank) signal appears to be stuck based on a lack of signal variation expected during normal operation, this DTC sets.

Conditions for Running the DTC

The engine is operating.

Conditions for Setting the DTC
    • The secondary fuel tank is not empty.
    • More than 241 km (150 miles) have been accumulated.
    • The PCM does not detect that the fuel level in the rear fuel tank moved by at least 3.0 liters (0.80 gallons).

OR

    • The secondary fuel tank is not empty.
    • The primary fuel tank is not full.
    • Engine operating more than 60 minutes.
    • The primary tank does not achieve the top of its range. Observe, after operating the engine for more than 60 minutes the fuel in the rear fuel tank will transfer to the front fuel tank.

OR

    • The secondary fuel tank is empty.
    • The primary fuel tank is full.
    • The fuel level in both fuel tanks does not change after traveling more than 284 km (200 miles). Observe, if the secondary fuel tank is empty, the primary fuel level should decrease after 284 km (200 miles).

Action Taken When the DTC Sets
    • The PCM stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
    • The vehicle fuel gauge displays empty.
    • The Check Gauge lamp illuminates.
    • The Driver Information Center displays a message.

Conditions for Clearing the DTC
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Use a scan tool in order to clear the DTC.

Diagnostic Aids

Important: 

   • Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the module. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
   • For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

Depending on the current fuel level, it may be difficult to locate a malfunctioning sending unit. The malfunction may only occur when the fuel level is full or near empty. The fuel sending unit may need to be removed for further diagnosis. A fuel level sensor that has an intermittent condition causes this DTC to set. Remove the fuel level sensor. Refer to Fuel Sender Assembly Replacement in order to test the resistance of the sensor. The resistance of the sensor should change from 40 to 250 ohms. Replace the sensor if the resistance did not change or was out of range.

The following occurs with this DTC set:

    • The vehicle fuel gauge displays empty.
    • The Check Gauge lamp illuminates.
    • The driver information center (DIC) displays a message.
    • The voltages in the Fuel Level Conversion Table are approximate values. Use this table to aid in diagnosis.

Fuel Level Conversion Table

Approximate Values

Fuel Level

Front Tank voltage

Rear Tank Voltage

100%

2.5V

2.5

75%

2.5V

1.5V

50%

2.5V

Less than 1V

25%

1.7V

Less than 1V

0%

Less than 1V

Less than 1V

    • If the fuel level sensor is operating OK, test the operation of the Balance Pump.
    •  For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Use DTC P0461 table if DTCs P0461 and P1431 set.

    2.

  2. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.

    3.

  3. This step determines if a circuit condition is causing the fuel level signal to be at a fixed value.

    4.

  4. This step determines if fuel is being delivered to the right fuel tank jet pump.

    The fuel pump will run for 2 seconds each time it is commanded ON with the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.

    5.

  5. This step determines if fuel is being transferred to the left fuel tank.

    The fuel pump runs for 2 seconds each time it is commanded ON with the scan tool. The fuel pump must be enabled several times to achieve the time specified in the diagnostic table.

    6.

  6. Foreign material in the fuel tank may cause the sensor to stick. Inspect the strainer for interfering with the float arm. A stuck sensor may not be apparent when the sensor is removed from the fuel tank. The following may have caused the DTCs to set:

    7. • The fuel tanks over filled.
    • Fuel level that is almost empty and then re-fueled with only a couple gallons.
    • The Fuel Level sender un-stuck while re-fueling.
    • The Fuel Level sender un-stuck on rough road or going around a corner.

  7. The PCM will not reset the mileage for this diagnostic if the fuel tanks are re-fueled to the same level as before the repair was made. Perform the following procedure in order to re-fuel the vehicle after replacing a sending unit or fuel tank.

    8. 1. Add 25 percent of the fuel that you removed before the repair.
    2. Start and idle the engine for 5 minutes.
    3. Turn OFF the engine.
    4. Add the remainder of the fuel.

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P0461 also set?

--

Go to DTC P0461 Fuel Level Sensor Performance

Go to Step 3

3

  1. Disconnect the right Fuel Level sensor electrical connector.
  2. Jumper the fuel level signal circuit to battery ground.
  3. Monitor the right Fuel Level sensor voltage parameter with the scan tool.

Is the right Fuel Level sensor voltage at the specified value?

0.0V

Go to Step 4

Go to Step 9

4

  1. Jumper the fuel level signal circuit and ground circuit together.
  2. Monitor the right Fuel Level sensor voltage parameter with the scan tool.

Is the right Fuel Level sensor voltage at the specified value?

0.0V

Go to Step 5

Go to Step 10

5

  1. Monitor the fuel level in the left tank with the scan tool.
  2. Add fuel if the left tank is empty.
  3. Disconnect the siphon jet pump feed pipe (black) from the right fuel tank.
  4. Insert the siphon jet pump fuel feed pipe into an approved gasoline container.
  5. Command the fuel pump ON for the specified time with the scan tool.
  6. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

10 seconds

300 ml   (0.633 pt)

Go to Step 6

Go to Step 11

6

Important: Inspect the fuel crossover hose if the right fuel tank is empty. Fuel flow to the right fuel tank is decreased during fueling if the crossover hose is collapsed or restricted.

  1. Connect the siphon jet pump fuel feed pipe (black) to the right fuel tank.
  2. Disconnect the siphon jet pump fuel return pipe (green) from the left fuel tank.
  3. Insert the siphon jet pump fuel return pipe into an approved gasoline container.
  4. Command the fuel pump ON for the specified time with the scan tool.
  5. Measure the volume of fuel.

Is the volume of fuel greater than the specified value?

8 seconds

332.6 ml  (0.703 pt)

Go to Step 7

Go to Step 12

7

  1. Remove the right tank fuel level sensor. Refer to Fuel Level Sensor Replacement .
  2. Inspect for the following:
    3. • A stuck Fuel Level sensor (i.e. the fuel strainer interfering with the sender float arm)
    • Fuel tank deformed
    • Foreign material in the fuel tank (ice)

Did you find and correct the condition?

--

Go to Step 16

Go to Step 8

8
  1. Connect the DMM between the fuel level sensor signal circuit and the fuel level sensor ground circuit (sensor side).
  2. Set the DMM to the 400ohms range.
  3. Sweep the fuel level sensor from stop to stop.

Does the resistance vary between the specified values?

40ohms (±1ohms) to 250ohms (±2.4ohms)

Go to Diagnostic Aids

Go to Step 13

9
  1. Disconnect the PCM connector C2 located on the opposite side of the manufacturer's logo. Refer to Powertrain Control Module Replacement .
  2. Test the right tank fuel level signal circuit for high resistance.
  3. If you find a condition, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

10
  1. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement .
  2. Test the right tank fuel level ground circuit for an open or for high resistance.
  3. If you find a condition, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

11

Inspect the siphon jet pump fuel feed pipe for restrictions and repair as necessary.

Is the action complete?

--

Go to Step 16

--

12

Inspect the siphon jet pump fuel return pipe for restrictions and repair as necessary.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

13

Replace the right tank fuel level sensor. Refer to Fuel Level Sensor Replacement .

Is the action complete?

--

Go to Step 16

--

14
  1. Inspect for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a poor connection, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

15

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 16

--

16

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear Information option with the scan tool.
  2. Start the engine and idle at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number with the scan tool.
  4. Operate vehicle within the Conditions for Running this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 17

Go to Step 2

17

Select the Capture Info option and the Review Info option with the scan tool.

Are any DTCs displayed that have not been diagnosed?

--

Go to Applicable DTC Table

System OK